Clinical experience using potassium-induced cardioplegia with hypothermia in aortic valve replacement

Abstract

Recent evidence suggests that use of potassium in concentrations of 15 to 50 mEq. per liter, in conjunction with hypothermia, to arrest the heart substantially minimizes the degree of injury during prolonged periods of myocardial anoxia. This method was employed in 54 patients undergoing aortic valve replacement. The mean age was 58 years. Aortic stenosis was the predominant lesion in 76 percent (41/54) and aortic incompetence in 24 percent (13/54). The mean cardiothoracic ratio was 0.61 ± 0.05 S.D. All patients were in New York Heart Association Functional Class III or IV. Myocardial temperature was maintained at less than 20° C. After aortic clamping, a 4° C. potassium chloride solution was injected into the aortic root or coronary ostia to arrest the heart. The mean cross-clamp time was 60 ± 9.0 minutes (S.D.). There was no death or electrocardiographic evidence of infarction. Enzymatic evidence of myocardial injury occurred in 3.7 percent (2/54), and 3.7 percent (2/54) required postoperative inotropic support. These data strongly suggest that the best method of myocardial preservation is a combination of potassium-induced arrest and hypothermia during prolonged aortic clamping.